The present invention relates to a vehicle intake manifold, and more particularly to an intake manifold having an adjustable plenum to provide variable runner length during engine operation.
An air intake manifold of a multi-cylinder engine is a branched pipe arrangement which connects the valve ports of each cylinder with an air inlet. The manifold may have considerable effect on engine performance. The intermittent or pulsating nature of the airflow through the manifold into each cylinder may develop resonances in the airflow at certain engine speeds. These may increase the volumetric efficiency and thus, the power at certain engine speeds, but may reduce such efficiency at other speeds, depending on manifold dimensions and shape.
Conventional intake manifolds for vehicles have a fixed air flow geometry. With a fixed intake system, the speed at which intake tuning occurs is also fixed. Since the engine operates over a broad RPM range, and since a different geometry may be ideal for different engine speeds, fixed geometry intake systems are designed with a geometry which is optimal for only a limited range of engine speeds. The intake is often designed as a compromise between torque at low speeds and horsepower at high speeds.
Various designs for variable intake geometry have met with varying degrees of success. Each of these conventional variable intake manifolds may be rather complex and expensive to produce. Servicing difficulty and limited variable tuning may also be disadvantageous design results of conventional variable intake manifolds.
Accordingly, it is desirable to provide a cost effective variable intake manifold which will operate with different types of engines and yet still maximize the variable tuning available during engine operation.